Catalytic and solvent processing for base oil production

ABSTRACT

Methods are provided for producing lubricant base oils using a combination of catalytic and solvent processing. By using a combination of catalytic processing for feed conversion and dewaxing while using solvent processing for removal of aromatics, Group II and Group III lubricant base oils can be produced using low pressure catalytic processes.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Provisional Application Ser.No. 62/097,649 filed Dec. 30, 2014, which is herein incorporated byreference in its entirety.

FIELD

Systems and methods are provided for production of lubricant oilbasestocks by a combination of catalytic and solvent processing.

BACKGROUND

Dewaxing is a commonly used technique for improving the properties of apetroleum fraction for use in various products, such as fuels orlubricant base stocks. Historically, solvent dewaxing was the first typeof dewaxing used for modifying the properties of a feedstock. Solventextraction and dewaxing allowed for separation of a feedstock into araffinate fraction for use as a distillate fuel or lubricant, anaromatics fraction, and a waxy fraction. More recently, catalyticdewaxing has been commonly used for improving the properties of feedsfor use in fuels or lubricant base stocks.

U.S. Pat. No. 4,259,170 describes a process for manufacturing lubebasestocks. In the process, one or more lower boiling fractions from avacuum distillation tower are solvent dewaxed to form lubricant basestocks. One or more higher boiling fractions are catalytically dewaxedin order to provide a pour point improvement for the higher boilingfractions that is greater than the amount that can be achieved bysolvent dewaxing.

U.S. Pat. No. 6,773,578 describes a process for preparing lubes withhigh viscosity index values. The process includes obtaining a firstfeedstock that includes at least 95% of material that boils below 1150°F. (621° C.), and a second feedstock that includes at least 95% ofmaterial that boils above 1150° F. (621° C.). The feedstock containingthe portion that boils below 1150° F. is catalytically dewaxed. Thefeedstock containing the portion that boils above 1150° F. is solventdewaxed and optionally also catalytically dewaxed. Performing solventdewaxing on the above 1150° F. portion is described as reducing thedifference between the cloud point and the pour point for the resultingproducts.

U.S. Patent Application Publication 2014/0042056 describes a process forpreparing multiple base oils from a feedstock. A lower boiling portionof a feedstock is catalytically dewaxed to form light neutral baseoil(s) while a higher boiling portion of a feedstock is solventprocessed to form heavy neutral or brightstock base oil(s).

U.S. Pat. No. 6,592,748 describes a raffinate hydroconversion process.After solvent extraction, the raffinate is exposed to a severehydroconversion process followed by a cold hydrofinishing process toform a lubricating oil basestock.

SUMMARY

In an aspect, a method for forming a lubricant base stock is provided,the method including hydroprocessing a feedstock having a T5 boilingpoint greater than about 600° F. (316° C.) and a sulfur content of atleast about 500 wppm under effective hydroprocessing conditions to forma hydroprocessed effluent, the effective hydroprocessing conditionsincluding a total pressure of less than about 1500 psig (10.3 MPag);separating the hydroprocessed effluent to form at least a gas phaseeffluent and a hydroprocessed liquid product effluent having a sulfurcontent of less than 500 wppm; dewaxing at least a first portion of thehydroprocessed liquid product effluent to form a dewaxed effluent;extracting at least a second portion of the hydroprocessed liquidproduct effluent in the presence of an extraction solvent to form araffinate product and an extract product, the raffinate product having asulfur content of about 300 wppm or less; and fractionating at least aportion of the raffinate product to form at least a lubricant base stockproduct having a viscosity index of at least about 80, and an aromaticscontent of about 3.0 wt % or less, or about 2.5 wt % or less, or about2.0 wt % or less, or about 1.5 wt % or less, or about 1.0 wt % or less.

In another aspect, a method for forming a lubricant base stock isprovided, the method including hydroprocessing a feedstock having a T5boiling point greater than about 600° F. (316° C.) and a sulfur contentof at least about 500 wppm under effective hydroprocessing conditions toform a hydroprocessed effluent, the effective hydroprocessing conditionsincluding a total pressure of less than about 1500 psig (10.3 MPag);separating the hydroprocessed effluent to form at least a gas phaseeffluent and a hydroprocessed liquid product effluent having a sulfurcontent of less than 500 wppm; exposing at least a portion of thehydroprocessed liquid product effluent to a dewaxing catalyst undereffective catalytic dewaxing conditions to form a dewaxed effluent, theeffective catalytic dewaxing conditions including a total pressure ofabout 300 psig (2.1 MPag) to about 700 psig (4.8 MPag); extracting atleast a portion of the dewaxed effluent in the presence of an extractionsolvent to form a raffinate product and an extract product, theraffinate product having a sulfur content of about 300 wppm or less; andfractionating at least a portion of the raffinate product to form atleast a lubricant base stock product having a viscosity index of atleast about 80, and an aromatics content of about 3.0 wt % or less, orabout 2.5 wt % or less, or about 2.0 wt % or less, or about 1.5 wt % orless, or about 1.0 wt % or less.

In still another aspect, a method for forming a lubricant base stock isprovided, the method including hydroprocessing a feedstock having a T5boiling point greater than about 600° F. (316° C.) and a sulfur contentof at least about 500 wppm under effective hydroprocessing conditions toform a hydroprocessed effluent; exposing at least a portion of thehydroprocessing effluent to a dewaxing catalyst under effectivecatalytic dewaxing conditions to form a hydroprocessed, dewaxedeffluent, the hydroprocessed, dewaxed effluent comprising a lubricantbase oil fraction having an aromatics content of at least about 3 wt %,the lubricant base oil fraction including a first lubricant base oilportion and a second lubricant base oil portion; exposing the firstlubricant base oil portion to an adsorbent to form an aromatics-depletedfirst lubricant base oil portion, the first lubricant base oil portioncomprising about 20 wt % to about 70 wt % of the lubricant base oilfraction, an aromatics content of the aromatics-depleted first lubricantbase oil portion being about 500 wppm or less; and combining thearomatics-depleted first lubricant base oil portion with the secondlubricant base oil portion.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically shows an example of a configuration suitable forprocessing a feedstock using both catalytic and solvent processing toform base oil products.

FIG. 2 schematically shows an example of a configuration for removingaromatics from a catalytically processed feed.

FIG. 3 shows a comparison of adsorbent selectivity for adsorption ofaromatics.

FIG. 4 shows a comparison of adsorbent capacity for adsorption ofaromatics.

DETAILED DESCRIPTION

All numerical values within the detailed description and the claimsherein are modified by “about” or “approximately” the indicated value,and take into account experimental error and variations that would beexpected by a person having ordinary skill in the art.

Overview

In various aspects, methods are provided for producing lubricant baseoils using a combination of catalytic and solvent processing. By using acombination of catalytic processing for feed conversion and dewaxingwhile using solvent processing for removal of aromatics, Group II andGroup III lubricant base oils can be produced using low pressurecatalytic processes. This can provide a variety of advantages. Oneadvantage of low pressure catalytic processing is that the amount ofhydrogen required for forming a lubricant base oil can be substantiallyreduced. In a conventional process, large hydrogen consumption and/orlarge hydrogen-containing treat gas rates are required in order toprovide sufficient aromatic saturation. By contrast, in various aspects,after catalytic processing at low pressure of a suitable feedstock forformation of lubricant base oil(s), a solvent extraction process can beused to reduce the aromatics content to a desired level, such as lessthan about 3.0 wt %, or less than about 2.5 wt %, or less than about 2.0wt %, or less than about 1.5 wt %, or less than about 1.0 wt %.

Conventionally, a feedstock for lubricant base oil production isprocessed either using solvent dewaxing or using catalytic dewaxing. Forexample, in a lube solvent plant, a vacuum gas oil (VGO) or anothersuitable feed is fractionated into light neutral (LN) and heavy neutral(HN) distillates and a bottom fraction by some type of vacuumdistillation. The bottoms fraction is subsequently deasphalted torecover an asphalt fraction and a deasphalted oil. The LN distillate, HNdistillate, and deasphalted oil are then solvent extracted to remove themost polar molecules as an extract and corresponding raffinates of LNdistillate, HN distillate, and deasphalted oil. The raffinates are thensolvent dewaxed to obtain dewaxed base oils of LN distillate, HNdistillate, and deasphalted oil with acceptable low temperatureproperties. It is beneficial to hydrofinish the lubricant basestockseither before or after the solvent dewaxing step. The resultinglubricant basestocks may contain a significant amount of aromatics (upto 50%) and high sulfur (>300 ppm). Thus, the typical base oils formedfrom solvent processing alone are Group I base stocks. As analternative, a raffinate hydroconversion step can be performed prior tothe solvent dewaxing. The hydroconversion is essentially a treatmentunder high H₂ pressure in presence of a metal sulfide basedhydroprocessing catalyst which removes most of the sulfur and nitrogen.The amount of conversion in the hydroconversion reaction is typicallytuned to obtain a predetermined increase in viscosity index andsaturates. This allows the solvent dewaxed lubricant base stock productsto be used as Group II or Group II+ base stocks. Optionally, the waxrecovered from a solvent dewaxing unit may also be processed bycatalytic dewaxing to produce Group III or Group III+ lubricant basestocks.

Current commercial methods for production of Group II and Group III baseoils typically use solvent processing in only a limited manner. With theexception of solvent deasphalting at early stages of handling a crudeoil fraction, processes for formation of Group II and Group III baseoils typically correspond to catalytic processes, such as hydrotreating,hydrocracking, catalytic dewaxing, and/or aromatic saturation (sometimesreferred to as hydrofinishing). Catalytic processing can be effectivefor producing Group II and Group III base oils having various viscosityindex, viscosity, and/or pour point values. However, in order to reducethe aromatics content of the lubricant base oils to a desired level,high pressure hydroprocessing is typically required. Hydrogen istypically a limited resource in a refinery setting, so processingimprovements that can allow for production of a high value product, suchas a lubricant base oil, while reducing or minimizing the hydrogenconsumption are highly desirable. Additionally, performing a sufficientamount of hydrocracking to reduce the aromatics content of a heavy oilfraction, such as a feed having at least 50 wt % of compounds with aboiling point of about 900° F. (482° C.) or more, can lead toovercracking of the heavy oil fraction.

In contrast to conventional methods, in various aspects a feedstocksuitable for forming lubricant base oil products can be processed in areaction system using catalytic processing to achieve desired levels ofheteroatom removal, viscosity index improvement, and pour pointreduction. A solvent extraction process can then be used to reduce thearomatics content to a desired level. For example, a vacuum gas oil orother suitable feedstock can be hydroprocessed (hydrotreated and/orhydrocracked) under sour conditions for heteroatom removal andoptionally for improvement of viscosity index and then catalyticallydewaxed (sweet or sour conditions) to improve cold flow properties. Thehydroprocessing can be performed at a pressure of 1500 psig (10.3 MPag),while the catalytic dewaxing can be performed at a pressure of about 700psig (4.8 MPag) or less. These pressures are substantially lower thanconventional conditions for catalytic processing of a lubricant baseoil. As a result, the effluent generated from the catalytic dewaxing hasa higher than expected aromatics content, such as an aromatics contentof about 5 wt % to about 30 wt %. The aromatics content is then reducedto less than about 3.0 wt %, or less than about 2.5 wt %, or less thanabout 2.0 wt %, or less than about 1.5 wt %, or less than about 1.0 wt%, using a solvent extraction process. Optionally, the dewaxed effluentand extracted effluent can be hydrofinished in suitable manner forproduction of a lubricant base oil. The extract from the solventextraction can also correspond to an upgraded product due to thehydroprocessing that occurs prior to the solvent extraction.

In some alternative aspects, instead of performing catalytic dewaxing,solvent dewaxing can be used. In such aspects, after the initialhydroprocessing, at least a portion of the hydroprocessed effluent canbe solvent extracted. The raffinate from extraction can then behydrofined followed by solvent dewaxing. Hydrofining conditions cancorrespond to hydrotreating conditions, hydrofinishing conditions, or acombination thereof.

In various additional or alternative aspects, methods are provided forusing an adsorbent to reduce the aromatics content of a potentiallubricant base oil. A feed being processed for lubricant base oilformation can end up with an excess amount of aromatics for a variety ofreasons. For example, during production of a Group II base oil, ahydrotreating process may be less effective than desired, resulting in apotential base oil after hydrotreating with an aromatics content of atleast about 3 wt %, or at least about 5 wt %. As another example, duringcatalytic processing to form a Group II base oil, the finalhydrofinishing catalyst for controlling aromatics content can deactivateover time. However, it may not be desirable to stop base oil productionto change out all or a portion of the catalyst. As a result, near theend of the useful processing lifetime for a hydrofinishing catalyst, thearomatics content of a resulting Group II or Group III base oil mayincrease.

In order to reduce the aromatics content of a potential lubricant baseoil to a desired amount, a portion of the effluent from the solventand/or catalytic process can be exposed to an adsorbent that is suitablefor adsorption of aromatics. Exposing only a portion of the effluent tothe adsorbent can provide a variety of advantages. For example, sinceonly a portion of the effluent is exposed to the adsorbent, the rate ofaccumulation of aromatics can be reduced, which can increase the timerequired between regeneration cycles for the adsorbent. Additionally,the aromatics separated from the effluent via adsorption can be capturedduring regeneration of the adsorbent as a separate aromatics-enrichedproduct stream. The portion of a lubricant base oil exposed to anadsorbent can be any convenient amount, such as about 20 wt % to 100 wt% of the lubricant base oil. In some aspects, the portion of thelubricant base oil can correspond to less than the full amount oflubricant base oil, such as about 20 wt % to about 70 wt %, and/or atleast about 40 wt %, and/or about 60 wt % or less.

Suitable adsorbents can include zeolite adsorbents, such as the NH4+exchanged form of zeolite Beta, or Ag impregnated USY. After adsorptionof a sufficient amount of aromatics, such as about 5 wt % to about 20 wt% of aromatics relative to the weight of the adsorbent, or about 5 wt %to about 15 wt %, or about 10 wt % to about 15 wt %, the adsorbent canbe regenerated by exposing the adsorbent to a desorption solvent.Toluene is an example of a suitable desorption solvent. Duringprocessing of a feed, multiple adsorbent beds can be used so that someadsorbent beds are active while other beds are being regenerated.

Group I basestocks or base oils are defined as base oils with less than90 wt % saturated molecules and/or at least 0.03 wt % sulfur content.Group I basestocks also have a viscosity index (VI) of at least 80 butless than 120. Group II basestocks or base oils contain at least 90 wt %saturated molecules and less than 0.03 wt % sulfur. Group II basestocksalso have a viscosity index of at least 80 but less than 120. Group IIIbasestocks or base oils contain at least 90 wt % saturated molecules andless than 0.03 wt % sulfur, with a viscosity index of at least 120. Inaddition to the above formal definitions, some Group I basestocks may bereferred to as a Group I+ basestock, which corresponds to a Group Ibasestock with a VI value of 103 to 108. Some Group II basestocks may bereferred to as a Group II+ basestock, which corresponds to a Group IIbasestock with a VI of at least 113. Some Group III basestocks may bereferred to as a Group III+ basestock, which corresponds to a Group IIIbasestock with a VI value of at least 140.

In a hydroprocessing reaction system, one way of characterizing areaction stage is based on the stage being a “sweet” reaction stage or a“sour” reaction stage. In this discussion, a reaction stage where thefeedstock passed into to the stage contains at least about 500 wppm ofsulfur, or at least about 1000 wppm of sulfur, can be referred to as a“sour” reaction stage. Optionally, the reaction stage can becharacterized based on the sulfur content of both the feedstock and anytreat gas passed into the reaction stage. A sour reaction stage can bein contrast to a “sweet” reaction stage, where the sulfur content in thefeedstock passed into the stage is about 500 wppm or less, or about 300wppm or less, or about 100 wppm or less, or about 50 wppm or less, orabout 15 wppm or less.

In this discussion, the severity of hydroprocessing performed on a feedcan be characterized based on an amount of conversion of the feedstock.In various aspects, the reaction conditions in the reaction system canbe selected to generate a desired level of conversion of a feed.Conversion of a feed is defined in terms of conversion of molecules thatboil above a temperature threshold to molecules below that threshold.The conversion temperature can be any convenient temperature. Forexample, for a lubricant base oil production process, a suitableconversion temperature can be from about 650° F. (343° C.) to about 750°F. (399° C.). Unless otherwise specified, the conversion temperature inthis discussion is a conversion temperature of 700° F. (371° C.).

In some aspects, using a final solvent extraction process to achieve adesired aromatics content can allow the severity of the initialhydroprocessing stage(s) to be reduced. For example, the amount ofconversion in the initial hydroprocessing stage can be about 10 wt % toless than about 30 wt % relative to a conversion temperature of 700° F.(371° C.). This is in contrast to a conventional lubricant productionprocess, which can typically require a conversion amount of from about30 wt % to about 50 wt % or more.

In the discussion below, a stage can correspond to a single reactor or aplurality of reactors. Optionally, multiple parallel reactors can beused to perform one or more of the processes, or multiple parallelreactors can be used for all processes in a stage. Each stage and/orreactor can include one or more catalyst beds containing hydroprocessingcatalyst. Note that a “bed” of catalyst in the discussion below canrefer to a partial physical catalyst bed. For example, a catalyst bedwithin a reactor could be filled partially with a hydrocracking catalystand partially with a dewaxing catalyst. For convenience in description,even though the two catalysts may be stacked together in a singlecatalyst bed, the hydrocracking catalyst and dewaxing catalyst can eachbe referred to conceptually as separate catalyst beds.

In the discussion herein, reference will be made to a hydroprocessingreaction system. The hydroprocessing reaction system corresponds to theone or more stages, such as two stages and/or reactors and an optionalintermediate separator, that are used to expose a feed to a plurality ofcatalysts under hydroprocessing conditions. The plurality of catalystscan be distributed between the stages and/or reactors in any convenientmanner, with some preferred methods of arranging the catalyst describedherein.

In this discussion, the distillate fuel boiling range is defined as 350°F. (177° C.) to 700° F. (371° C.). Distillate fuel boiling rangeproducts can include products suitable for use as kerosene products(including jet fuel products) and diesel products, such as premiumdiesel or winter diesel products. In this discussion, the naphthaboiling range is defined as 36° C. (97° F.) to about 177° C. (350° F.).

Feedstocks

A wide range of petroleum and chemical feedstocks can be hydroprocessedin accordance with the disclosure. Suitable feedstocks include whole andreduced petroleum crudes, atmospheric and vacuum residua, deasphaltedresidua, cycle oils, FCC tower bottoms, gas oils, including vacuum gasoils and coker gas oils, light to heavy distillates including raw virgindistillates, hydrocrackates, hydrotreated oils, slack waxes,Fischer-Tropsch waxes, raffinates, and mixtures of these materials.

One way of defining a feedstock is based on the boiling range of thefeed. One option for defining a boiling range is to use an initialboiling point for a feed and/or a final boiling point for a feed.Another option, which in some instances may provide a morerepresentative description of a feed, is to characterize a feed based onthe amount of the feed that boils at one or more temperatures. Forexample, a “T5” boiling point for a feed is defined as the temperatureat which 5 wt % of the feed will boil off. Similarly, a “T95” boilingpoint is a temperature at 95 wt % of the feed will boil.

Typical feeds include, for example, feeds with an initial boiling pointof at least about 650° F. (343° C.), or at least about 700° F. (371°C.), or at least about 750° F. (399° C.). Alternatively, a feed may becharacterized using a T5 boiling point, such as a feed with a T5 boilingpoint of at least about 650° F. (343° C.), or at least about 700° F.(371° C.), or at least about 750° F. (399° C.). In some aspects, thefinal boiling point of the feed can be at least about 1100° F. (593°C.), such as at least about 1150° F. (621° C.) or at least about 1200°F. (649° C.). In other aspects, a feed may be used that does not includea large portion of molecules that would traditional be considered asvacuum distillation bottoms. For example, the feed may correspond to avacuum gas oil feed that has already been separated from a traditionalvacuum bottoms portion. Such feeds include, for example, feeds with afinal boiling point of about 1150° F. (621° C.), or about 1100° F. (593°C.) or less, or about 1050° F. (566° C.) or less. Alternatively, a feedmay be characterized using a T95 boiling point, such as a feed with aT95 boiling point of about 1150° F. (621° C.) or less, or about 1100° F.(593° C.) or less, or about 1050° F. (566° C.) or less. An example of asuitable type of feedstock is a wide cut vacuum gas oil (VGO) feed, witha T5 boiling point of at least about 700° F. (371° C.) and a T95 boilingpoint of about 1100° F. or less. Optionally, the initial boiling pointof such a wide cut VGO feed can be at least about 700° F. and/or thefinal boiling point can be at least about 1100° F. It is noted thatfeeds with still lower initial boiling points and/or T5 boiling pointsmay also be suitable, so long as sufficient higher boiling material isavailable so that the overall nature of the process is a lubricant baseoil production process and/or a fuels hydrocracking process.

The above feed description corresponds to a potential feed for producinglubricant base oils. In some aspects, methods are provided for producingboth fuels and lubricants. When fuels are an additional desired product,feedstocks with lower boiling components may also be suitable. Forexample, a feedstock suitable for fuels production, such as a lightcycle oil, can have a T5 boiling point of at least about 350° F. (177°C.), such as at least about 400° F. (204° C.). Examples of a suitableboiling range include a boiling range of from about 350° F. (177° C.) toabout 700° F. (371° C.), such as from about 390° F. (200° C.) to about650° F. (343° C.). Thus, a portion of the feed used for fuels andlubricant base oil production can include components having a boilingrange from about 170° C. to about 350° C. Such components can be part ofan initial feed, or a first feed with a T5 boiling point of about 650°F. (343° C.) can be combined with a second feed, such as a light cycleoil, that includes components that boil between 200° C. and 350° C.

Many typical feeds for production of lubricant base oils can have asubstantial sulfur content. For example, the sulfur content of a feedprior to exposing the feed to hydroprocessing for heteroatom removal canbe at least about 300 ppm by weight of sulfur, or at least about 500wppm, or at least about 1000 wppm, or at least about 2000 wppm, or atleast about 4000 wppm, or at least about 10,000 wppm, or at least about20,000 wppm. Typical feeds can also have substantial aromatics content.Prior to exposing the feed to hydroprocessing, the aromatics content ofa feed can be at least about 10 wt %, or at least about 15 wt %, or atleast about 20 wt %, or at least about 30 wt %, or at least about 40 wt%. After any catalytic processing, the aromatics content of thecatalytically processed effluent can be about 5 wt % to about 30 wt % orabout 5 wt % to about 25 wt %, or about 5 wt % to about 20 wt %, orabout 5 wt % to about 15 wt %, or about 10 wt % to about 30 wt %, orabout 10 wt % to about 25 wt %, or about 10 wt % to about 20 wt %, orabout 10 wt % to about 15 wt %, or about 15 wt % to about 30 wt %, orabout 15 wt % to about 25 wt %, or about 15 wt % to about 20 wt %.

In some embodiments, at least a portion of the feed can correspond to afeed derived from a biocomponent source. In this discussion, abiocomponent feedstock refers to a hydrocarbon feedstock derived from abiological raw material component, from biocomponent sources such asvegetable, animal, fish, and/or algae. Note that, for the purposes ofthis document, vegetable fats/oils refer generally to any plant basedmaterial, and can include fat/oils derived from a source such as plantsof the genus Jatropha. Generally, the biocomponent sources can includevegetable fats/oils, animal fats/oils, fish oils, pyrolysis oils, andalgae lipids/oils, as well as components of such materials, and in someembodiments can specifically include one or more type of lipidcompounds. Lipid compounds are typically biological compounds that areinsoluble in water, but soluble in nonpolar (or fat) solvents.Non-limiting examples of such solvents include alcohols, ethers,chloroform, alkyl acetates, benzene, and combinations thereof.

In some aspects, it may be desirable to fractionate a feedstock forlubricant base oil production so that different portions of the feed canbe processed under different conditions. This can be one method forforming at least two lubricant base oil products from a feedstock. Forexample, a suitable feedstock can be separated to form at least a lowerboiling feedstock portion, a higher boiling feedstock portion, and abottoms portion. Such a separation can be performed, for example, usinga vacuum distillation unit. One method for determining the amounts inthe various portions is by selecting cut point temperatures. The cutpoint temperatures may vary depending on the nature of the feedstock.Generally, the cut point between the lower boiling portion and thehigher boiling portion can be between about 850° F. (454° C.) and 950°F. (510° C.), such as at least about 875° F. (468° C.) or less thanabout 925° F. (496° C.) or less than about 900° F. (482° C.). The cutpoint between the higher boiling portion and the bottoms portion can bebetween about 1050° F. (566° C.) and about 1150° F. (621° C.), such asless than about 1100° F. (593° C.). In some alternative aspects, it maybe desirable to increase the relative amount of light neutral base oilsthat are produced. In such aspects, the cut point between the lowerboiling portion and the higher boiling portion may be higher, such as atleast about 950° F. (510° C.), or at least about 1000° F. (538° C.), andless than about 1150° F. (621° C.), such as less than about 1100° F.(593° C.) or less than about 1050° F. (566° C.).

It is noted that the above fractionation temperatures represent thesplit between lighter feedstock portions, heavier feedstock portions,and a bottoms portion. If desired, additional fractions could also beformed based on additional cut points. For the purposes of thediscussion herein, any such additional fractions can be processedaccording to boiling range. Thus, if additional fractions are formedwith a T95 boiling point of less than about 850° F. (454° C.) to about950° F. (510° C.), all such additional fractions would be processed aspart of the lower boiling feedstock portion.

Hydroprocessing for Base Oil Production

After optional separation in a vacuum distillation apparatus, afeedstock for lubricant base oil production can be passed into ahydroprocessing reaction system. An initial stage of the reaction systemcan be used for contaminant removal to produce a hydroprocessed effluenthaving a sulfur content of about 100 wppm or less, or about 50 wppm orless, or about 15 wppm or less. A separation can then be performed toremove lower boiling portions of the hydroprocessed effluent. Thisseparation can remove compounds that are gasses at standard temperatureand pressure (such as H₂S, NH₃, and C₄— compounds), or the separationcan remove a portion of the effluent that corresponds to naphtha and/ordistillate fuel boiling range compounds. The remaining liquid portion ofthe effluent can then be catalytically dewaxed. Due to the separation,the catalytic dewaxing step can be performed under sweet processingconditions.

The hydroprocessing (hydrotreating and/or hydrocracking) conditions inthe reaction system can also be selected to generate a desired level ofconversion of a feed. Conversion of the feed can be defined in terms ofconversion of molecules that boil above a temperature threshold tomolecules below that threshold. The conversion temperature can be anyconvenient temperature, such as about 700° F. (371° C.). In an aspect,the amount of conversion in the stage(s) of the reaction system can beselected to enhance diesel production while achieving a substantialoverall yield of fuels. The amount of conversion can correspond to thetotal conversion of molecules within a stage of the reaction system thatis used to catalytically process the feed for lubricant base oilproduction. Suitable amounts of conversion of molecules boiling above700° F. to molecules boiling below 700° F. include converting at leastabout 5 wt % of the 700° F.+ portion of the feedstock in thehydroprocessing stage(s), or at least about 10 wt %, or at least about15 wt %, or at least about 20%, or at least about 25% of the 700° F.+portion. Additionally or alternately, the amount of conversion for thereaction system can be about 35% or less, or about 30% or less, or about25% or less, or about 20% or less. Still larger amounts of conversionmay also produce a suitable effluent for forming lubricant base oils,but such higher conversion amounts will also result in a reduced yieldof lubricant base oils. Reducing the amount of conversion can increasethe yield of lubricant base oils, but reducing the amount of conversionto below the ranges noted above may result in a catalytically processedeffluent that is not suitable for formation of Group II or Group IIIlubricant base oils. In various aspects, the catalytic dewaxing stage(s)of the reaction system can convert about 1 wt % to about 10 wt % of feedto the dewaxing stage(s), such as about 1 wt % to about 5 wt %.

Hydrotreatment Conditions

Heteroatoms can be removed from a feedstock under effectivehydrotreatment conditions, effective hydrocracking conditions, or acombination thereof. Hydrotreatment is typically used to reduce thesulfur, nitrogen, and aromatic content of a feed. The catalysts used forhydrotreatment can include conventional hydroprocessing catalysts, suchas those that comprise at least one Group VIII non-noble metal (Columns8-10 of IUPAC periodic table), preferably Fe, Co, and/or Ni, such as Coand/or Ni; and at least one Group VI metal (Column 6 of IUPAC periodictable), preferably Mo and/or W. Such hydroprocessing catalysts cancomprise transition metal sulfides that are impregnated or dispersed ona refractory support or carrier such as alumina and/or silica. Thesupport or carrier itself typically has no significant/measurablecatalytic activity. Alternatively, the catalyst can correspond to asubstantially carrier- or support-free catalyst, commonly referred to asa bulk catalyst.

For a supported hydrotreating catalyst, any convenient support materialcan be used. In addition to alumina and/or silica, other suitablesupport/carrier materials can include, but are not limited to, zeolites,titania, silica-titania, and titania-alumina. Suitable aluminas areporous aluminas such as gamma or eta having average pore sizes from 50to 200 Å, or 75 to 150 Å; a surface area from 100 to 300 m²/g, or 150 to250 m²/g; and a pore volume of from 0.25 to 1.0 cm³/g, or 0.35 to 0.8cm³/g. More generally, any convenient size, shape, and/or pore sizedistribution for a catalyst suitable for hydrotreatment of a distillate(including lubricant base oil) boiling range feed in a conventionalmanner may be used. It is within the scope of the present disclosurethat more than one type of hydroprocessing catalyst can be used in oneor multiple reaction vessels.

The at least one Group VIII non-noble metal, in oxide form, cantypically be present in an amount ranging from about 2 wt % to about 40wt %, preferably from about 4 wt % to about 15 wt %. The at least oneGroup VI metal, in oxide form, can typically be present in an amountranging from about 2 wt % to about 70 wt %, preferably for supportedcatalysts from about 6 wt % to about 40 wt % or from about 10 wt % toabout 30 wt %. These weight percents are based on the total weight ofthe catalyst. Suitable metal catalysts include cobalt/molybdenum (1-10%Co as oxide, 10-40% Mo as oxide), nickel/molybdenum (1-10% Ni as oxide,10-40% Co as oxide), or nickel/tungsten (1-10% Ni as oxide, 10-40% W asoxide) on alumina, silica, silica-alumina, or titania.

The hydrotreatment is carried out in the presence of hydrogen. Ahydrogen stream is, therefore, fed or injected into a vessel or reactionzone or hydroprocessing zone in which the hydroprocessing catalyst islocated. Hydrogen, which is contained in a hydrogen “treat gas,” isprovided to the reaction zone. Treat gas, as referred to in thisdisclosure, can be either pure hydrogen or a hydrogen-containing gas,which is a gas stream containing hydrogen in an amount that issufficient for the intended reaction(s), optionally including one ormore other gasses (e.g., nitrogen and light hydrocarbons such asmethane), and which will not adversely interfere with or affect eitherthe reactions or the products. Impurities, such as H₂S and NH₃ areundesirable and would typically be removed from the treat gas before itis conducted to the reactor. The treat gas stream introduced into areaction stage will preferably contain at least about 50 vol. % and morepreferably at least about 75 vol. % hydrogen, or at least about 80 vol %hydrogen, or at least about 90 vol % hydrogen.

Effective hydrotreating conditions can include temperatures of 200° C.to 450° C., or 315° C. to 425° C.; liquid hourly space velocities (LHSV)of 0.1 hr⁻¹ to 10 hr⁻¹; and hydrogen treat rates of 200 scf/B (35.6m³/m³) to 10,000 scf/B (1781 m³/m³), or 500 (89 m³/m³) to 5,000 scf/B(890.5 m³/m³). With regard to pressure, the hydrotreating can beperformed at a pressure of about 300 psig (2.1 MPag) to about 1500 psig(10.4 MPag), or about 750 psig (5.2 MPag) to about 1500 psig (10.4MPag), or about 1000 psig (6.9 MPag) to about 1500 psig (10.4 MPag), orabout 1200 psig (8.3 MPag) to about 1500 psig (10.4 MPag).

Hydrocracking Conditions

In addition to or as an alternative to hydrotreating, hydrocracking canbe used to hydroprocess a feed for heteroatom removal. Hydrocrackingcatalysts typically contain sulfided base metals on acidic supports,such as amorphous silica alumina, acidic zeolites such as USY, oracidified alumina. Often these acidic supports are mixed or bound withother metal oxides such as alumina, titania or silica. Examples ofsuitable acidic supports include acidic molecular sieves, such aszeolites or silicoaluminophophates. One example of suitable zeolite isUSY, such as a USY zeolite with cell size of 24.25 Angstroms or less.Additionally or alternately, the catalyst can be a low acidity molecularsieve, such as a USY zeolite with a Si to Al ratio of at least about 20,and preferably at least about 40 or 50. Zeolite Beta is another exampleof a potentially suitable hydrocracking catalyst. Non-limiting examplesof metals for hydrocracking catalysts include metals or combinations ofmetals that include at least one Group VIII metal, such as nickel,nickel-cobalt-molybdenum, cobalt-molybdenum, nickel-tungsten,nickel-molybdenum, and/or nickel-molybdenum-tungsten. Support materialswhich may be used for can comprise a refractory oxide material such asalumina, silica, alumina-silica, kieselguhr, diatomaceous earth,magnesia, zirconia, or combinations thereof, with alumina, silica,alumina-silica being the most common (and preferred, in one embodiment).In some aspects, a hydrotreating catalyst as described above can beexposed to a feed under effective hydrocracking conditions to performhydrocracking on a feed.

In various aspects, effective hydrocracking conditions for ahydrocracking process can include temperatures of about 550° F. (288°C.) to about 840° F. (449° C.), liquid hourly space velocities of from0.05 h⁻¹ to 10 h⁻¹, and hydrogen treat gas rates of from 35.6 m³/m³ to1781 m³/m³ (200 SCF/B to 10,000 SCF/B). In other embodiments, theconditions can include temperatures in the range of about 600° F. (343°C.) to about 815° F. (435° C.), liquid hourly space velocities of from0.05 h⁻¹ to 10 h⁻¹, and hydrogen treat gas rates of from about 213 m³/m³to about 1068 m³/m³ (1200 SCF/B to 6000 SCF/B). With regard to pressure,the hydrocracking can be performed at a pressure of about 300 psig (2.1MPag) to about 1500 psig (10.4 MPag), or about 750 psig (5.2 MPag) toabout 1500 psig (10.4 MPag), or about 1000 psig (6.9 MPag) to about 1500psig (10.4 MPag), or about 1200 psig (8.3 MPag) to about 1500 psig (10.4MPag).

Catalytic Dewaxing Process

After hydrotreating and/or hydrocracking for heteroatom removal, atleast a (liquid) portion of the resulting effluent can be catalyticallydewaxed for improvement of pour point and/or other cold flow properties.Suitable dewaxing catalysts can include molecular sieves such ascrystalline aluminosilicates (zeolites). In some aspects, anyconventional dewaxing catalyst can be used. In other aspects, themolecular sieve can comprise, consist essentially of, or be ZSM-5,ZSM-22, ZSM-23, ZSM-35, ZSM-48, zeolite Beta, or a combination thereof,for example ZSM-23 and/or ZSM-48, or ZSM-48 and/or zeolite Beta.Optionally but preferably, molecular sieves that are selective fordewaxing by isomerization as opposed to cracking can be used, such asZSM-48, zeolite Beta, ZSM-23, or a combination thereof. Additionally oralternately, the molecular sieve can comprise, consist essentially of,or be a 10-member ring 1-D molecular sieve. Examples include EU-1,ZSM-35 (or ferrierite), ZSM-11, ZSM-57, NU-87, SAPO-11, ZSM-48, ZSM-23,and ZSM-22. Preferred materials are EU-2, EU-11, ZBM-30, ZSM-48, orZSM-23. ZSM-48 is most preferred. Note that a zeolite having the ZSM-23structure with a silica to alumina ratio of from about 20:1 to about40:1 can sometimes be referred to as SSZ-32. Other molecular sieves thatare isostructural with the above materials include Theta-1, NU-10,EU-13, KZ-1, and NU-23. Optionally but preferably, the dewaxing catalystcan include a binder for the molecular sieve, such as alumina, titania,silica, silica-alumina, zirconia, or a combination thereof, for examplealumina and/or titania or silica and/or zirconia and/or titania.

Preferably, the dewaxing catalysts used in processes according to thedisclosure are catalysts with a low ratio of silica to alumina. Forexample, for ZSM-48, the ratio of silica to alumina in the zeolite canbe less than about 200:1, such as less than about 110:1, or less thanabout 100:1, or less than about 90:1, or less than about 75:1. Invarious embodiments, the ratio of silica to alumina can be from 50:1 to200:1, such as 60:1 to 160:1, or 70:1 to 100:1.

In various embodiments, the catalysts according to the disclosurefurther include a metal hydrogenation component. The metal hydrogenationcomponent is typically a Group VI and/or a Group VIII metal. Preferably,the metal hydrogenation component is a Group VIII noble metal.Preferably, the metal hydrogenation component is Pt, Pd, or a mixturethereof. In an alternative preferred embodiment, the metal hydrogenationcomponent can be a combination of a non-noble Group VIII metal with aGroup VI metal. Suitable combinations can include Ni, Co, or Fe with Moor W, preferably Ni with Mo or W.

The metal hydrogenation component may be added to the catalyst in anyconvenient manner. One technique for adding the metal hydrogenationcomponent is by incipient wetness. For example, after combining azeolite and a binder, the combined zeolite and binder can be extrudedinto catalyst particles. These catalyst particles can then be exposed toa solution containing a suitable metal precursor. Alternatively, metalcan be added to the catalyst by ion exchange, where a metal precursor isadded to a mixture of zeolite (or zeolite and binder) prior toextrusion.

The amount of metal in the catalyst can be at least 0.1 wt % based oncatalyst, or at least 0.15 wt %, or at least 0.2 wt %, or at least 0.25wt %, or at least 0.3 wt %, or at least 0.5 wt % based on catalyst. Theamount of metal in the catalyst can be 20 wt % or less based oncatalyst, or 10 wt % or less, or 5 wt % or less, or 2.5 wt % or less, or1 wt % or less. For embodiments where the metal is Pt, Pd, another GroupVIII noble metal, or a combination thereof, the amount of metal can befrom 0.1 to 5 wt %, preferably from 0.1 to 2 wt %, or 0.25 to 1.8 wt %,or 0.4 to 1.5 wt %. For embodiments where the metal is a combination ofa non-noble Group VIII metal with a Group VI metal, the combined amountof metal can be from 0.5 wt % to 20 wt %, or 1 wt % to 15 wt %, or 2.5wt % to 10 wt %.

Process conditions in a catalytic dewaxing zone can include atemperature of from 200 to 450° C., preferably 270 to 400° C., an LHSVfrom about 0.2 h⁻¹ to about 10 h⁻¹, such as from about 0.5 h⁻¹ to about5 h⁻¹, and a treat gas rate of from 35.6 m³/m³ (200 SCF/B) to 1781 m³/m³(10,000 scf/B), preferably 178 m³/m³ (1000 SCF/B) to 890.6 m³/m³ (5000SCF/B). With regard to pressure, the dewaxing can be performed at apressure of about 300 psig (2.1 MPag) to about 700 psig (4.8 MPag), orabout 300 psig (2.1 MPag) to about 600 psig (4.2 MPag), or about 300psig (2.1 MPag) to about 500 psig (3.5 MPag), or about 400 psig (2.8MPag) to about 700 psig (4.8 MPag), or about 400 psig (2.8 MPag) toabout 600 psig (4.2 MPag), or about 400 psig (2.8 MPag) to about 500psig (3.5 MPag), or about 500 psig (3.5 MPag) to about 700 psig (4.8MPag).

Hydrofinishing and/or Aromatic Saturation Process

In some optional aspects, a hydrofinishing and/or aromatic saturationstage can also be provided. If a solvent extraction stage is present foraromatics removal, then typically a hydrofinishing stage will not beincluded. However, a hydrofinishing stage may be desirable if the finalaromatics removal step is via adsorption rather than by solventextraction.

Hydrofinishing and/or aromatic saturation catalysts can includecatalysts containing Group VI metals, Group VIII metals, and mixturesthereof. In an embodiment, preferred metals include at least one metalsulfide having a strong hydrogenation function. In another embodiment,the hydrofinishing catalyst can include a Group VIII noble metal, suchas Pt, Pd, or a combination thereof. The mixture of metals may also bepresent as bulk metal catalysts wherein the amount of metal is about 30wt. % or greater based on catalyst. Suitable metal oxide supportsinclude low acidic oxides such as silica, alumina, silica-aluminas ortitania, preferably alumina. The preferred hydrofinishing catalysts foraromatic saturation will comprise at least one metal having relativelystrong hydrogenation function on a porous support. Typical supportmaterials include amorphous or crystalline oxide materials such asalumina, silica, and silica-alumina. The support materials may also bemodified, such as by halogenation, or in particular fluorination. Themetal content of the catalyst is often as high as about 20 weightpercent for non-noble metals. In an embodiment, a preferredhydrofinishing catalyst can include a material belonging to the M41Sclass or family of catalysts. The M41S family of catalysts aremesoporous materials having high silica content. Examples includeMCM-41, MCM-48 and MCM-50. A preferred member of this class is MCM-41.If separate catalysts are used for aromatic saturation andhydrofinishing, an aromatic saturation catalyst can be selected based onactivity and/or selectivity for aromatic saturation, while ahydrofinishing catalyst can be selected based on activity for improvingproduct specifications, such as product color and polynuclear aromaticreduction.

Hydrofinishing conditions can include temperatures from about 125° C. toabout 425° C., preferably about 180° C. to about 280° C., a hydrogenpartial pressure from about 500 psig (3.4 MPa) to about 3000 psig (20.7MPa), preferably about 1500 psig (10.3 MPa) to about 2500 psig (17.2MPa), and liquid hourly space velocity from about 0.1 hr⁻¹ to about 5hr⁻¹ LHSV, preferably about 0.5 hr⁻¹ to about 1.5 hr⁻¹. Additionally, ahydrogen treat gas rate of from 35.6 m³/m³ to 1781 m³/m³ (200 SCF/B to10,000 SCF/B) can be used.

Solvent Extraction for Aromatics Removal

Solvent extraction can be used to reduce the aromatics content and/orthe amount of polar molecules in the hydroprocessed, dewaxed effluent.The solvent extraction process selectively dissolves aromatic componentsto form an aromatics-rich extract phase while leaving the moreparaffinic components in an aromatics-poor raffinate phase. Naphthenesare distributed between the extract and raffinate phases. Typicalsolvents for solvent extraction include phenol, furfural and N-methylpyrrolidone. More generally, any convenient solvent for removingaromatics to about 2.5 wt % or less, or about 1.5 wt % or less, or about1.0 wt % or less, can be used. However, use of those solvents mostselective for removing aromatics, such as SO₂, sulfolane, and DMSO, canmaximize both yield of the raffinate and concentration of aromatics inthe extract phase. Such selective solvents, by accentuating thedifference in density between the dispersed and continuous phases, tendto overcome low rates in the coalescence step of the extraction process.By controlling the solvent to oil ratio, extraction temperature, contentof water or other solvency modifier, temperature gradient in theliquid-liquid treater tower, and method of contacting hydroprocessed,dewaxed effluent to be extracted with solvent, one can further controlthe degree of separation between the extract and raffinate phases. Anyconvenient type of liquid-liquid extractor can be used, such as acounter-current liquid-liquid extractor.

In various aspects, a suitable extraction solvent can have one or moreof the following characteristics, such as two or more, or three or more,or four or more, or all of the characteristics. One characteristic canbe a high polarity or high dipole moment. A solvent with a high polaritycan often correspond to a solvent with a high boiling point and/or ahigh dipole moment. Another characteristic can be thermal and/orchemical stability under the solvent extraction conditions, which caninvolve elevated temperatures. Still another characteristic can besuitable miscibility with water, with organic solvents, or a combinationthereof. Yet another characteristic can be a solvent which presents areduced or minimized hazard from a fire and/or toxicological standpoint.In other words, the solvent can have properties such as a high flashpoint temperature (thereby reducing or minimizing fire hazard) or a lowcorrosiveness (thereby reducing or minimizing toxicological hazard).Still another desirable solvent characteristic can be to have a solventthat is substantially free of contaminants, such as a solvent with apurity of at least about 95 vol %, or at least about 99 vol %.

Examples of solvents that correspond to one or more of the abovecharacteristics can include, but are not limited to, methyl pyrollidone(NMP), furfural, phenol, SO₂, sulfolane, dimethylsulfoxide, orcombinations thereof. In some aspects, a solvent can further contain asolvency modifier, such as water.

Example of Configuration for Integrated Reaction System

FIG. 1 shows a schematic example of configuration for forming lubricantbase oils using both catalytic processing and solvent processing. In theconfiguration shown in FIG. 1, a feedstock for lubricant base oilproduction 105 is introduced into a vacuum distillation tower 110. Thevacuum distillation tower 110 fractionates the feedstock 105 into atleast a portion 115 suitable for further processing to form a lubricantbase oil. The feedstock portion 115 is then hydroprocessed 120 (i.e.,hydrotreated and/or hydrocracked) to form a hydroprocessed effluent 125.The hydroprocessed effluent 125 can be separated (not shown) to removeat least gas phase heteroatom contaminants generated duringhydroprocessing, such as H₂S and NH₃. A remaining portion of thehydroprocessed effluent 125, such as a liquid portion, can then becatalytically dewaxed 130 to form a hydroprocessed, dewaxed effluent135. The hydroprocessed, dewaxed effluent 135 can then be solventextracted 140. This results in an aromatics-rich extract 148 and araffinate 145 with reduced aromatics content. The raffinate 145 can havean aromatics content of less than about 2.5 wt %, or less than about 1.5wt %, or less than about 1.0 wt %, making the raffinate suitable for useas a Group II or Group III lubricant base oil, optionally after furtherhydrofinishing. The aromatics-rich extract 148 represents a high qualityextract product based on the low sulfur content. Additionally, it isbelieved that the extract 148 can have a narrower distribution of carbonatoms per molecule and be more stable to oxidative and thermaldegradation than a typical extract derived from solvent processing toform a Group I base oil.

It is noted that after hydroprocessing, the order of performingadditional processes on the hydroprocessed effluent 125 can be any oneof a variety of convenient orderings. For example, the configuration inFIG. 1 shows a liquid portion of hydroprocessed effluent 125 beingcatalytically dewaxed 130. This produces a hydroprocessed, dewaxedeffluent 135 which is then solvent extracted 140. As an alternative (notshown), the liquid portion of the hydroprocessed effluent 125 can besolvent extracted 140 to produce an aromatics-rich extract and araffinate with a reduced aromatics content. The hydroprocessed raffinatecan then be catalytically dewaxed to produce a dewaxed effluent that issuitable for use as a Group II or Group III lubricant base oil,optionally after further hydrofinishing. The aromatics-rich extractgenerated in this alternative configuration can have properties similarto those described above for aromatics-rich extract 148 in theconfiguration shown in FIG. 1.

Example 1 Solvent Extraction of a Catalytically Processed Lubricant BaseOil Feed

In the following example, a solvent extraction process was modeled foran example of a lubricant base oil feed. The modeled feed correspondedto an output stream from a hydrocracking process. The feed contained 24%aromatics and had a density @ 15° C. of 0.8895 g/cc. The D2887 boilingpoints of the feed were between 340° C. (IBP) to 600° C. (FBP). Themodeled feed did not include sulfur or nitrogen.

An empirical-based model was then used to determine the output streamsfrom performing an aromatic extraction process on the modeled feed undervarious extraction conditions. In the modeled extraction, an extractorwas used that had 5 to 10 theoretical stages. In the modeled extraction,the dosage solvent was between 300 to 500 vol % of the feed, the waterin the solvent was between 0.5 to 1.5 wt %, the temperature gradient wasbetween 5 to 10° C., and the bottom temperature was between 75 to 90° C.The extraction was based on use of n-methyl pyrollidone (NMP) as thesolvent. The modeled results showed an aromatic content in the raffinateof between ˜0.5% to 1.7% depending on the conditions.

Example 2 Comparison with Conventional Catalytic Processing

The following example provides a qualitative yield and productcomparison between a conventional configuration and a process forcombined catalytic and solvent processing.

For a typical commercial Group II lubricant base oil production process,a hydrocracking unit can be operated between 2000 psig and 3000 psigpressure. This typically results in conversion of around 50 wt % of thefeedstock relative to a 700° F. conversion temperature. The hydrocrackedfeed can then be dewaxed in the presence of a dewaxing catalyst. Sometypical Group II lubricant base oil production process can have about 5wt % conversion in the catalytic dewaxing process. As an example, atypical expected lube production yield for such a conventionalconfiguration can be about 47.5 vol % based on the volume of feed passedinto the hydrocracking unit.

In some aspects, a hydrocracking and/or hydrotreating process can beused to hydroprocess a feed for lubricant base oil production to reducethe sulfur and nitrogen contents of the feed. The hydrocracking and/orhydrotreating process can also provide some increase in viscosity indexfor the eventual lubricant base oil process. However, because solventextraction will be used for aromatics reduction, the conversion in thehydrocracking and/or hydrotreating stage can be lower than aconventional process. For example, the conversion in the hydroprocessingstage relative to a conversion temperature of 700° F. can be about 30 wt% or less. The hydroprocessed effluent (or at least a portion of theeffluent) can then be catalytically dewaxed. This can result in about 5wt % conversion of the hydroprocessed effluent, which is similar to theconversion in the dewaxing stage of a conventional process. Thehydroprocessed, dewaxed effluent can then be solvent extracted toproduce an aromatics-rich extract and a raffinate with a reducedaromatics content of about 2.5 wt % or less, or about 1.5 wt % or less,or about 1.0 wt % or less. The extraction unit can also improve thestability of the lubricant base oil product by removing polynucleararomatics (PNAs). The total lube production for this configuration canbe about 33 vol % relative to the feed to the hydroprocessing stage.However, the aromatics-rich extract stream produced in thisconfiguration can also have a volume of about 33 vol % relative to thefeed to the hydroprocessing stage. The aromatics-rich extract stream canbe a premium stream since it will have low sulfur and nitrogen contentand less aromatic than traditional extract streams formed duringprocessing of a Group I lubricant base oil. In addition, this extractwill be more stable and have a more narrow carbon distributioncomposition than traditional extracts of Group I lube production.

In an alternative aspect where the hydroprocessing stage corresponds toa hydrotreating stage, the conversion can be about 15 wt % or less, orabout 10 wt % or less. Use of this type of alternative can be dependenton the nature of the initial feedstock available in a refinery. In thistype of alternative, assuming a 50% efficiency in the solvent extractionunit(s), the overall yield can be about 43 vol % of Group II qualitylubricant base oil, with a similar amount of premium aromatics-richextract.

Example 3 Adsorbents for Aromatics Removal

In some alternative aspects, methods are also provided for using anadsorbent to remove aromatics from a catalytically processed lubricantbase oil product while also generating an aromatics-rich side product.In such aspects, a portion of a lubricant base oil product can be passedthrough an adsorbent to remove aromatics. The aromatics-depleted portioncan then be recombined with the remaining portion so that the overallproduct has a desired aromatics content. As an example, a lubricant baseoil production process may generate 35 kilobarrels per day (kbd) oflubricant base oil. A portion of this production, such as 20 kbd, can bepassed through the adsorbent. The adsorbent can be effective forreducing the aromatics concentration of the 20 kbd portion to a lowlevel, such as less than about 500 wppm, or less than about 100 wppm.The aromatics-lean portion of the lubricant base oil can then berecombined with the remaining 15 kbd of the lubricant base oil. If theoriginal aromatics content was, for example, about 7 wt %, the finallubricant base oil can have an aromatics content of about 3 wt %.

An advantage of the adsorbent process is that the adsorbent can be usedas needed. For example, at the beginning of a processing run, thearomatics content of the lubricant base oil may be within a desiredspecification. As one or more catalysts deactivate, the aromaticscontent may increase. The adsorbent can then be used on a portion of thelubricant base oil product to maintain a desired specification.

After a period of adsorption, the adsorbent may reach a maximum desiredloading of aromatics. This can correspond to, for example, about 10 wt %to about 20 wt % of aromatics relative to the weight of the adsorbent.The adsorbent vessel can then be taken off-line to allow forregeneration. The regeneration can be performed by passing a desorptionsolvent through the adsorbent, such as toluene. The aromaticsconcentrate produced during the desorption cycle can be sent to anextraction unit as feed to recover all the remaining paraffinicmolecules or also as feed to Treated Distillate Aromatic Extract for thetire or asphalt industry or used as a solvency additive.

FIG. 2 schematically shows a configuration for using an adsorbent aspart of a process for making a lubricant base oil. In FIG. 2, a portionof a lubricant base oil product 205 is passed into an adsorbent vessel.In the configuration shown in FIG. 2, either adsorbent vessel 240 or 241can be in use for adsorption at any given time. During adsorption from alubricant base oil, passing the portion of lubricant base oil product205 through the adsorbent vessel (such as adsorbent vessel 240) producesan aromatics-lean product 215. The aromatics-lean product 215 can thenbe combined with the remaining portion of the lubricant base oil (notshown).

While an adsorbent vessel is not in use for adsorption, such asadsorbent vessel 241, at least a portion of the time can be used forregenerating the adsorbent vessel. In the configuration shown in FIG. 2,during a regeneration cycle, a fresh stream of desorption solvent 222can be passed into adsorbent vessel 241. This results in desorption ofaromatics from the adsorbent in vessel 241 to form an aromatics extractstream 245. A surge tank 250 can be used to control the flow ofaromatics extract stream 245 to fractionator or stripper 260. Thefractionator 260 can be used to separate the aromatics extract from thedesorption solvent, resulting in formation of an aromatic concentrationstream 265 and a recycled desorption solvent stream 262.

The adsorption methods described herein can generally be used with anylubricant base oil product where a partial reduction of aromaticscontent is desired. The adsorbent can be any adsorbent that is selectivefor adsorption of aromatics relative to paraffins and naphthenes.Molecular sieves can be suitable adsorbents, such as zeolite H-Beta andAg/USY or other zeolites (5A, 13X, MCM-22, MCM-68 and ZSM-5). Theabsorbents could also include active carbons, mesoporous silica, M41Sfamily of materials, sulfonated polymers such as Amberlyst acid ionexchanged resin, Nafion, It is believe that adsorption primarily occurson the surface and temperature may influence the diffusion of largearomatic molecules through viscous liquids. Key parameters of desirableadsorbent are related to acidity, pore size and mesoporous/macroporousnature. A metal cation modified adsorbent may also impact oncapacity/separation factor of aromatic adsorption. Some suitable metalscations can include, but are not limited to, Ag+, Na+, Ca2+, and Cu+. Inthis discussion, a metal cation can be identified by simply referring toa cation of the corresponding metal, such as by referring to a cation ofAg, Na, Ca, or Cu, without explicitly reciting an oxidation state.

The adsorption and desorption processes can be performed at temperaturesfrom about 80° C. to about 300° C. The amount of desorption solvent canbe about 1 g of solvent per g of adsorbent used. As a comparison, eachkg of adsorbent is suitable for treating about 2000 barrels of lubricantbase oil.

Example 4 Adsorption of a Catalytically Processed Lubricant Base OilFeed

In the following example, an adsorption process was applied for making alubricant base oil feed with improved saturate content. Thehydroprocessed and dewaxed feed corresponded to an output stream from ahydrocracking/dewaxing process. These feed properties are summarized inthe table below.

TABLE 1 Properties of a lube basestock to be treated via adsorption:Property (Test Method) Result Result KV100, KV40 (D445) 5.28 cSt, 29.26cSt 5.3 cSt, 29.1 cSt Density (D4052) 0.8527 g/mL 0.854 g/mL Flashpoint(D92) 226° C. 218° C. Total Aromatics (M1514) 63.12 86 (mmol/kg) 1+Ring, mmol/kg 53.8 73.3 2+ Ring, mmol/kg 6.96 9.8 3+ Ring, mmol/kg 0.571.1 4+ Ring, mmol/kg 1.99 2.9

As the first pass of adsorbent screening, 3 g of feed was charged into abatch multi-wells unit with varied adsorbent loadings (100 mg to 800mg). Various absorbents were tested with 24 hours run-length at 30° C.The liquid product was recovered and submitted for aromatics measurementby UV-Vis. In adsorption data analysis, lube basestock feed was taken asa binary mixture containing all aromatic molecules lumped together as asingle entity and non-aromatic molecules being the other component. Thecapacity and selectivity of adsorbent were calculated using directexperimental measurements of total moles & composition of liquid beforeand after contact with adsorbent, and adsorbent loading. These twoadsorption parameters are defined as the adsorption separation factor(S12) and the adsorbent capacity (g aromatic adsorbed/100 g Adsorbent).Over a group of adsorbents screened using the static experiments, H-Betaand 5 wt % Ag/USY showed preferential adsorption of aromatic moleculesover saturates. As shown is FIG. 3, maximum average separation factorS12 was significant for H-Beta and 5 wt % Ag/USY. For H-Beta and 5 wt %Ag/USY, the S12 for 1-ring aromatic molecules over saturates wasobserved to be ˜9-10. The adsorbent capacity for H-Beta and 5 wt %Ag/USY was also determined to be ˜4, as illustrated in FIG. 4.

Any convenient cycle can be used for adsorption and/or regeneration. Forexample, adsorption of aromatics can be performed by filling theadsorbent vessel, holding the base oil in the vessel for a period oftime, emptying the vessel, filling the vessel with the desorptionsolvent, and then holding the desorption solvent for a period of time.Using this type of schedule, the empty/fill portion of the schedule cancorrespond to about 30 minutes, while the holding time (for lubricantbase oil or for desorption solvent) can be about 2 hours. The adsorptionand/or desorption processes can be performed at isothermal(approximately constant temperature) or non-isothermal conditions.

Additional Embodiments Embodiment 1

A method for forming a lubricant base stock, comprising: hydroprocessinga feedstock having a T5 boiling point greater than about 600° F. (316°C.) and a sulfur content of at least about 500 wppm under effectivehydroprocessing conditions to form a hydroprocessed effluent, theeffective hydroprocessing conditions including a total pressure of lessthan about 1500 psig (10.3 MPag); separating the hydroprocessed effluentto form at least a gas phase effluent and a hydroprocessed liquidproduct effluent having a sulfur content of less than 500 wppm; dewaxingat least a first portion of the hydroprocessed liquid product effluentto form a dewaxed effluent; extracting at least a second portion of thehydroprocessed liquid product effluent in the presence of an extractionsolvent to form a raffinate product and an extract product, theraffinate product having a sulfur content of about 300 wppm or less; andfractionating at least a portion of the raffinate product to form atleast a lubricant base stock product having a viscosity index of atleast about 80, and an aromatics content of about 3.0 wt % or less, orabout 2.5 wt % or less, or about 2.0 wt % or less, or about 1.5 wt % orless, or about 1.0 wt % or less.

Embodiment 2

The method of Embodiment 1, further comprising hydrofining at least aportion of the raffinate product under effective hydrofining conditionsto form a hydrofined raffinate, wherein dewaxing at least a firstportion of the hydroprocessed liquid product effluent comprises solventdewaxing at least a portion of the hydrofined raffinate.

Embodiment 3

The method of Embodiment 1, wherein dewaxing at least a first portion ofthe hydroprocessed liquid product effluent comprises exposing the atleast a first portion of the hydroprocessed liquid product effluent to adewaxing catalyst under effective catalytic dewaxing conditions to formthe dewaxed effluent, the effective catalytic dewaxing conditionsincluding a total pressure of about 300 psig (2.1 MPag) to about 700psig (4.8 MPag), wherein extracting at least a second portion of thehydroprocessed liquid product effluent comprises extracting at least aportion of the dewaxed effluent.

Embodiment 4

A method for forming a lubricant base stock, comprising: hydroprocessinga feedstock having a T5 boiling point greater than about 600° F. (316°C.) and a sulfur content of at least about 500 wppm under effectivehydroprocessing conditions to form a hydroprocessed effluent, theeffective hydroprocessing conditions including a total pressure of lessthan about 1500 psig (10.3 MPag); separating the hydroprocessed effluentto form at least a gas phase effluent and a hydroprocessed liquidproduct effluent having a sulfur content of less than 500 wppm; exposingat least a portion of the hydroprocessed liquid product effluent to adewaxing catalyst under effective catalytic dewaxing conditions to forma dewaxed effluent, the effective catalytic dewaxing conditionsincluding a total pressure of about 300 psig (2.1 MPag) to about 700psig (4.8 MPag); extracting at least a portion of the dewaxed effluentin the presence of an extraction solvent to form a raffinate product andan extract product, the raffinate product having a sulfur content ofabout 300 wppm or less; and fractionating at least a portion of theraffinate product to form at least a lubricant base stock product havinga viscosity index of at least about 80, and an aromatics content ofabout 3.0 wt % or less, or about 2.5 wt % or less, or about 2.0 wt % orless, or about 1.5 wt % or less, or about 1.0 wt % or less.

Embodiment 5

The method of Embodiments 3 or 4, wherein the effective dewaxingconditions comprise a total pressure of about 300 psig (2.1 MPag) toabout 600 psig (4.2 MPag), or about 300 psig (2.1 MPag) to about 500psig (3.5 MPag), or about 400 psig (2.8 MPag) to about 700 psig (4.8MPag), or about 400 psig (2.8 MPag) to about 600 psig (4.2 MPag), orabout 400 psig (2.8 MPag) to about 500 psig (3.5 MPag), or about 500psig (3.5 MPag) to about 700 psig (4.8 MPag), the effective dewaxingconditions optionally being effective for conversion of about 1 wt % toabout 10 wt % of the at least a portion of the hydroprocessed liquidproduct effluent, or about 1 wt % to about 5 wt %.

Embodiment 6

The method of any of Embodiments 3 to 5, wherein the dewaxed effluenthas an aromatics content of about 5 wt % to about 30 wt % or about 5 wt% to about 25 wt %, or about 5 wt % to about 20 wt %, or about 5 wt % toabout 15 wt %, or about 10 wt % to about 30 wt %, or about 10 wt % toabout 25 wt %, or about 10 wt % to about 20 wt %, or about 10 wt % toabout 15 wt %, or about 15 wt % to about 30 wt %, or about 15 wt % toabout 25 wt %, or about 15 wt % to about 20 wt %.

Embodiment 7

The method of any of the above embodiments, further comprisinghydrofinishing at least a portion of the dewaxed effluent undereffective hydrofinishing conditions.

Embodiment 8

The method of any of the above embodiments, wherein fractionating the atleast a portion of the raffinate product further comprises forming adistillate boiling range product.

Embodiment 9

The method of any of the above embodiments, further comprisingseparating the dewaxed effluent to form a fraction having a T5 boilingpoint of at least about 500° F. and at least one fuel product, the atleast one fuel product being a naphtha boiling range product or adistillate fuel boiling range product, wherein extracting at least aportion of the dewaxed effluent comprises extracting at least a portionof the fraction having a T5 boiling point of at least about 500° F.(260° C.).

Embodiment 10

The method of any of the above embodiments, wherein separating thehydroprocessed effluent further comprises forming at least one fuelproduct, the at least one fuel product being a naphtha boiling rangeproduct or a distillate fuel boiling range product.

Embodiment 11

The method of any of the above embodiments wherein the effectivehydroprocessing conditions comprise a total pressure of about 300 psig(2.1 MPag) to about 1500 psig (10.4 MPag), or about 750 psig (5.2 MPag)to about 1500 psig (10.4 MPag), or about 1000 psig (6.9 MPag) to about1500 psig (10.4 MPag), or about 1200 psig (8.3 MPag) to about 1500 psig(10.4 MPag), the hydroprocessed liquid product effluent optionallyhaving a sulfur content of about 100 wppm or less, or about 50 wppm orless, or about 15 wppm or less.

Embodiment 12

The method of any of the above embodiments, wherein the effectivehydroprocessing conditions comprise effective hydrotreating conditions,effective hydrocracking conditions, or a combination thereof, theeffective hydroprocessing conditions optionally being effective forconversion of about 5 wt % to about 30 wt % of the feedstock having a T5boiling point greater than about 600° F. (316° C.) relative to aconversion temperature of about 700° F. (371° C.), or about 10 wt % toabout 25 wt %, or about 10 wt % to about 20 wt %, or about 5 wt % toabout 15 wt %, or about 5 wt % to about 10 wt %.

Embodiment 13

The method of any of the above embodiments, wherein the extractionsolvent comprises methyl pyrollidone (NMP), furfural, phenol, SO₂,sulfolane, dimethylsulfoxide, or a combination thereof.

Embodiment 14

A method for forming a lubricant base stock, comprising: hydroprocessinga feedstock having a T5 boiling point greater than about 600° F. (316°C.) and a sulfur content of at least about 500 wppm under effectivehydroprocessing conditions to form a hydroprocessed effluent; exposingat least a portion of the hydroprocessing effluent to a dewaxingcatalyst under effective catalytic dewaxing conditions to form ahydroprocessed, dewaxed effluent, the hydroprocessed, dewaxed effluentcomprising a lubricant base oil fraction having an aromatics content ofat least about 3 wt %, the lubricant base oil fraction including a firstlubricant base oil portion and a second lubricant base oil portion;exposing the first lubricant base oil portion to an adsorbent to form anaromatics-depleted first lubricant base oil portion, the first lubricantbase oil portion comprising about 20 wt % to about 70 wt % of thelubricant base oil fraction, an aromatics content of thearomatics-depleted first lubricant base oil portion being about 500 wppmor less; and combining the aromatics-depleted first lubricant base oilportion with the second lubricant base oil portion.

Embodiment 15

The method of Embodiment 14, wherein the adsorbent comprises one or moreof zeolites, active carbon, mesoporous silica, materials correspondingto the M41S family of materials, and sulfonated polymers, the adsorbentoptionally comprising one or more of zeolite Beta, USY, zeolite 5A,zeolite 13X, MCM-22, MCM-68, ZSM-5, MCM-41, Amberlyst acid ion exchangedresin and Nafion, the adsorbent optionally further comprising metalcations, the metal cations optionally comprising cations of Ag, Na, Ca,Cu, or a combination thereof.

Embodiment 16

The method of Embodiments 14 or 15, further comprising exposing theadsorbent to a desorption solvent to form an aromatics extract fraction.

Embodiment 17

The method of any of Embodiments 14 to 16, further comprisinghydrofinishing at least a portion of the hydroprocessed, dewaxedeffluent to form a hydrofinished effluent, the hydrofinished effluentcomprising the lubricant base oil fraction.

When numerical lower limits and numerical upper limits are listedherein, ranges from any lower limit to any upper limit are contemplated.While the illustrative embodiments of the disclosure have been describedwith particularity, it will be understood that various othermodifications will be apparent to and can be readily made by thoseskilled in the art without departing from the spirit and scope of thedisclosure. Accordingly, it is not intended that the scope of the claimsappended hereto be limited to the examples and descriptions set forthherein but rather that the claims be construed as encompassing all thefeatures of patentable novelty which reside in the present disclosure,including all features which would be treated as equivalents thereof bythose skilled in the art to which the disclosure pertains.

The present disclosure has been described above with reference tonumerous embodiments and specific examples. Many variations will suggestthemselves to those skilled in this art in light of the above detaileddescription. All such obvious variations are within the full intendedscope of the appended claims.

What is claimed is:
 1. A method for forming a lubricant base stock,comprising: hydroprocessing a feedstock having a T5 boiling pointgreater than 600° F. (316° C.) and a sulfur content of at least 500 wppmunder effective hydroprocessing conditions to form a hydroprocessedeffluent, the effective hydroprocessing conditions including a totalpressure of less than 1500 psig (10.3 MPag); separating thehydroprocessed effluent to form at least a gas phase effluent and ahydroprocessed liquid product effluent having a sulfur content of lessthan 500 wppm; dewaxing at least a first portion of the hydroprocessedliquid product effluent to form a dewaxed effluent; extracting at leasta second portion of the hydroprocessed liquid product effluent in thepresence of an extraction solvent to form a raffinate product and anextract product, the raffinate product having a sulfur content of 300wppm or less; and fractionating at least a portion of the raffinateproduct to form at least a lubricant base stock product having aviscosity index of at least 80, and an aromatics content of 2.5 wt % orless.
 2. The method of claim 1, wherein dewaxing at least a firstportion of the hydroprocessed liquid product effluent comprises exposingthe at least a first portion of the hydroprocessed liquid producteffluent to a dewaxing catalyst under effective catalytic dewaxingconditions to form the dewaxed effluent, the effective catalyticdewaxing conditions including a total pressure of 300 psig (2.1 MPag) to700 psig (4.8 MPag), wherein extracting at least a second portion of thehydroprocessed liquid product effluent comprises extracting at least aportion of the dewaxed effluent.
 3. The method of claim 2, wherein theeffective dewaxing conditions comprise a total pressure of 400 psig (2.8MPag) to 600 psig (4.2 MPag), the effective dewaxing conditions areeffective for conversion of 1 wt % to 10 wt % of the at least a portionof the hydroprocessed liquid product effluent, or a combination thereof4. The method of claim 2, wherein the dewaxed effluent has an aromaticscontent of 5 wt % to 30 wt %.
 5. The method of claim 1, furthercomprising hydrofining at least a portion of the raffinate product undereffective hydrofining conditions to form a hydrofined raffinate, whereindewaxing at least a first portion of the hydroprocessed liquid producteffluent comprises solvent dewaxing at least a portion of the hydrofinedraffinate.
 6. The method of claim 1, further comprising hydrofinishingat least a portion of the dewaxed effluent under effectivehydrofinishing conditions.
 7. The method of claim 1, whereinfractionating the at least a portion of the raffinate product furthercomprises forming a distillate boiling range product.
 8. The method ofclaim 1, further comprising separating the dewaxed effluent to form afraction having a T5 boiling point of at least 500° F. (260° C.) and atleast one fuel product, the at least one fuel product being a naphthaboiling range product or a distillate fuel boiling range product,wherein extracting at least a portion of the dewaxed effluent comprisesextracting at least a portion of the fraction having a T5 boiling pointof at least 500° F. (260° C.).
 9. The method of claim 1, whereinseparating the hydroprocessed effluent further comprises forming atleast one fuel product, the at least one fuel product being a naphthaboiling range product or a distillate fuel boiling range product. 10.The method of claim 1, wherein the effective hydroprocessing conditionscomprise a total pressure of 750 psig (5.2 MPag) to 1500 psig (10.4MPag), the effective hydroprocessing conditions comprise effectivehydrotreating conditions or effective hydrocracking conditions, or acombination thereof.
 11. The method of claim 1, wherein the effectivehydroprocessing conditions are effective for conversion of 5 wt % to 30wt % of the feedstock having a T5 boiling point greater than 600° F.(316° C.) relative to a conversion temperature of 700° F. (371° C.). 12.The method of claim 1, wherein the hydroprocessed liquid producteffluent has a sulfur content of 100 wppm or less.
 13. The method ofclaim 1, wherein the extraction solvent is methyl pyrollidone (NMP),furfural, phenol, SO₂, sulfolane, dimethylsulfoxide, or combinationthereof.
 14. A method for forming a lubricant base stock, comprising:hydroprocessing a feedstock having a T5 boiling point greater than 600°F. (316° C.) and a sulfur content of at least 500 wppm under effectivehydroprocessing conditions to form a hydroprocessed effluent, theeffective hydroprocessing conditions including a total pressure of lessthan 1500 psig; separating the hydroprocessed effluent to form at leasta gas phase effluent and a hydroprocessed liquid product effluent havinga sulfur content of less than 500 wppm; exposing at least a portion ofthe hydroprocessed liquid product effluent to a dewaxing catalyst undereffective catalytic dewaxing conditions to form a dewaxed effluent, theeffective catalytic dewaxing conditions including a total pressure of300 psig to 700 psig; extracting at least a portion of the dewaxedeffluent in the presence of an extraction solvent to form a raffinateproduct and an extract product, the raffinate product having a sulfurcontent of 300 wppm or less; and fractionating at least a portion of theraffinate product to form at least a lubricant base stock product havinga viscosity index of at least 80, and an aromatics content of 2.5 wt %or less.
 15. A method for forming a lubricant base stock, comprising:hydroprocessing a feedstock having a T5 boiling point greater than 600°F. (316° C.) and a sulfur content of at least 500 wppm under effectivehydroprocessing conditions to form a hydroprocessed effluent; exposingat least a portion of the hydroprocessing effluent to a dewaxingcatalyst under effective catalytic dewaxing conditions to form ahydroprocessed, dewaxed effluent, the hydroprocessed, dewaxed effluentcomprising a lubricant base oil fraction having an aromatics content ofat least 3 wt %, the lubricant base oil fraction including a firstlubricant base oil portion and a second lubricant base oil portion;exposing the first lubricant base oil portion to an adsorbent to form anaromatics-depleted first lubricant base oil portion, the first lubricantbase oil portion comprising 20 wt % to 70 wt % of the lubricant base oilfraction, an aromatics content of the aromatics-depleted first lubricantbase oil portion being 500 wppm or less; and combining thearomatics-depleted first lubricant base oil portion with the secondlubricant base oil portion.
 16. The method of claim 15, wherein theadsorbent comprises one or more of zeolites, active carbon, mesoporoussilica, materials corresponding to the M41S family of materials, andsulfonated polymers.
 17. The method of claim 15, wherein the adsorbentcomprises one or more of zeolite Beta, USY, zeolite 5A, zeolite 13X,MCM-22, MCM-68, ZSM-5, MCM-41, Amberlyst acid ion exchanged resin andNafion.
 18. The method of claim 15, wherein the adsorbent comprisesmetal cations, the metal cations comprising cations of Ag, Na, Ca, Cu,or a combination thereof.
 19. The method of claim 15, further comprisingexposing the adsorbent to a desorption solvent to form an aromaticsextract fraction.
 20. The method of claim 15, further comprisinghydrofinishing at least a portion of the hydroprocessed, dewaxedeffluent to form a hydrofinished effluent, the hydrofinished effluentcomprising the lubricant base oil fraction.